Lloyd A. Weber

The vapor pressure of 1,1,1,2-tetrafluoroethane (R134a) and chlorodifluoromethane (R22)

We measured the vapor pressure of chlorodifluoromethane (commonly known as R22) at temperatures between 217.1 and 248.5 K and of 1,1,1,2-tetrafluoroethane (commonly known as R134a) in the temperature range 214.4 to 264.7 K using a comparative ebulliometer. For 1,1,1,2-tetrafluoroethane at pressures between 220.8 and 1017.7kPa (corresponding to temperatures in the range 265.6 to 313.2K), additional measurements were made with a Burnett apparatus. We have combined our results for 1,1,1,2-tetrafluoroethane with those already published from this laboratory at higher pressures to obtain a smoothing equation for the vapor pressure from 215 K to the critical temperature. For chlorodifluoromethane our results have been combined with certain published results to provide an equation for the vapor pressure at temperatures from 217 K to the critical temperature.

Estimating the virial coefficients of small polar molecules

We adapt existing models for estimating the second and third virial coefficients of small molecules to the halogenated methanes and ethanes. We compare the results with the abundant new, high-qualityPVT data resulting from the search for alternative refrigerants. The present model provides an accurate method for calculating densities, and therefore it should provide reliable thermodynamic properties and fugacity coefficients. We give equations and parameters useful for estimating the properties of pure refrigerants and their mixtures when noPVT data are available.

Measurements of the virial coefficients and equation of state of the carbon dioxide+ethane system in the supercritical region

Gas-phase densities of the system carbon dioxide+ethane were measured with a Burnett apparatus at 320 K and at pressures up to approximately 10 MPa. Measurements were made on systems having carbon dioxide mole fractions of 0, 0.25166, 0.49245, 0.73978, and 1. Second and third virial coefficients were determined for each composition, and the cross virial coefficients were calculated. Comparisons were made with other recent high-quality measurements on this system. For each mixture compositionPρT measurements were made on five isochores having densities within ±30% of the critical density. Temperatures varied from 288 to 320 K. The two-phase boundary was determined and estimates are given forTc andPc for each composition.

Thermodynamic properties of CF3CHFCHF2, 1,1,1,2,3,3-hexafluoropropane

We report the thermodynamic properties of 1,1,1,2,3,3-hexafluoropropane (known in the refrigeration industry as R236ea or HFC-236ea) in the temperature and pressure region commonly encountered in thermal machinery. The properties are based on measurements of the vapor pressure, the density of the compressed liquid (PVT), the refractive index of the saturated liquid and vapor, the critical temperature, and the speed of sound in the vapor phase. The surface tension was determined from the capillary rise. From these data we deduce the ideal-gas heat-capacity, the saturated liquid and vapor densities, the equation of state of the vapor phase, the surface tension, and estimates of the critical pressure and density. The data determine the coefficients for a Carnahan-Starlings-DeSantis (CSD) equation of state. The CSD coefficients found in REFPROP 4.0 database are based on these present measurements.

The virial coefficients of five binary mixtures of fluorinated methanes and ethanes

We have made new measurements of the gas-phasePVT surface of five binary mixtures of hydrofluorocarbons (HFCs) in a Burnett/isochoric apparatus. The components chosen all have moderate to large reduced dipole moments. We presentPVT data, derived mixture virial coefficients, cross second virial coefficients, and binary interaction parameters for these systems, and we compare the results with a recently published model for calculating second and third viral coefficients of polar gases and their mixtures. That model accounts for the polar nature of the molecules with a term containing the reduced dipole moment,μR, and it contains mixing rules for the substance-specific parameters needed to calculate the second and third cross virial coefficients. The model and data are in satisfactory agreement. and the model can be used to greatly extend the useful range of the limited set of data.

Ebulliometric measurement of the vapor pressures of R123 and R141b

Abstract We have used the technique of comparative ebulliometry to measure the vapor pressures of several alternative refrigerants. A description is given of a simple apparatus that was built for this purpose, and results are reported for the vapor pressures of R123 and R141b. Data cover the range 270 K to 312 K at pressures from 25 to 129 kPa. The results are compared with published data.

Thermodynamic properties of 1,1-dichloro-1-fluoroethane (R141b)

Abstract Defibaugh D.R., Goodwin A.R.H., Morrison G. and Weber L.A., 1993. Thermodynamic properties of 1,1-dichloro-1-fluoroethane (R141b). Fluid Phase Equilibria 85: 271-284. Thermodynamic properties of 1,1-dichloro-1-fluoroethane (R141b) were measured using a vibrating-tube densimeter and two different ebulliometric techniques. The densimeter was used to measure compressed liquid densities, and the ebulliometers were used to study the vapor pressure. Measurements of the density were made between 278 and 369 K and between 100 and 6000 kPa. The vapor pressure was measured from 253 to 355 K at pressures from 10 to 449 kPa. Both the compressed liquid and the vapor pressure results are compared with other published data. Our results for the vapor pressure have been combined with results already published to obtain a correlation for the vapor pressure from 253 K to the critical point.

The vapor pressure of 1, 1-dichloro-2, 2, 2-trifluoroethane (R123)

The vapor pressure of 1, 1-dichloro-2, 2, 2-trifluoroethane (R123) has been measured at temperatures between 256.4 and 453.8 K by ebulliometric and static techniques. These results have been combined to obtain a correlation for the vapor pressure from 256.4 K to the critical temperature.

Design of a high-pressure ebulliometer, with vapor-liquid equilibrium results for the systems CHF2 Cl + CF3 CH3 and CF3 CH2 F + CH2F2

We describe the design and operation of a new high-pressure metal ebulliometer which can operate at pressures to at least 3 MPa in the range 220–400 K. Infinite-dilution activity coefficients are presented for the system CHF2Cl + CF3-CH, at 275 K and for the system CF3-CH2F + CH2F2, at 260, 230, and 300 K. The Wilson activity coellicient model and a virial coefficient model are applied to these systems, and the phase equilibrium conditions are calculated. The results are shown to agree well with predicted and with published measured values. The excess enthalpy is calculated and compared with results from a Peng Robinson equation of state. Vapor densities on the dew curves are given.

Critical parameters and saturation densities of 1,1-dichloro-2,2,2-trifluoroethane

Abstract An optical cell has been used to determine the critical parameters, Tc and ϱc, and densities along the liquid—vapor phase boundary of 1,1-dichloro-2,2,2-trifluoroethane (Refrigerant 123). The critical temperature was found to be 456.87 K and the critical density is 550 kg/m3. The critical pressure was calculated from vapor pressure data to be 36.74 bar, which yields a value of 0.269 for the critical compressibility factor, Zc. Measurement temperatures varied from 298 K to the critical point for the saturated liquid and from 433 K to the critical point for saturated vapor.